Improvements in image processing technology and CPU performance have allowed for the incorporation of digital image technology into various electronic devices. In particular, cellular phones and personal digital assistants (PDA's) have been marketed with image processing technology which allows for the capture of digital images via an internal image sensor and controller, e.g., a digital camera. Image processing technology can also be incorporated into other electronic devices such as calculators, computers, watches, pagers, walkie-talkies and the like.
Image processing technology incorporates the use of semiconductor components for capturing light images and processing same in digital form within the electronic device. Image sensors are known to be constructed using various technologies, for example, CMOS (complementary metal oxide semiconductor) and CCD (charged coupled device). In certain applications such as cellular phones, it is preferred to use CMOS image sensors, notwithstanding that CCD image sensors provide higher quality. In this regard, CMOS image sensors require less power consumption, can be fabricated using semiconductor processing techniques at lower costs than those used in fabricating CCD image sensors, can be operated by a single power supply with lower power consumption than that of CCD image sensors, and use integrated logic circuits in the image sensor chip thereby minimizing package size in comparison with CCD image sensors. Examples of CMOS image sensors and manufacturing methods are described in U.S. Pat. Nos. 6,610,557 and 6,727,487, the disclosures of which are incorporated herein by reference.
In cellular phone applications, thickness of the image sensor package is important because of the lens housing which is added on top of the package for the electronic device. Today, a typical camera module thickness (package plus lens housing) is about 10 mm. In order to minimize camera module thickness, there is being developed new technology to achieve thinner camera modules and packages. Image sensor packages using chip scale package (CSP) technology are becoming a typical trend in the package industry. In addition, solder ball joint reliability is becoming an important factor for image sensor CSP development.
Accordingly, there is the need for improvements in image sensor package technology in order to minimize camera module thickness, as well as enhancing solder joint reliability. These attributes of the present invention are achieved by the construction of the image sensor package and method of fabrication as described hereinafter.